1. Field of the Invention
The present invention relates to fingerprint sensor apparatuses and, more particularly, to a fingerprint sensor apparatus in which a fingerprint sensor element formed on a semiconductor element is packaged in a state where the fingerprint sensor element is exposed on the surface of the finger sensor apparatus.
While electronic information communication spreads, a demand of performing individual recognition in electronic equipment is increasing so as to protect confidentiality of personal information. Although various techniques have been developed as personal identification means and put in practical use, a technique for discriminating fingerprints has attracted attention among them.
2. Description of the Related Art
A fingerprint sensor apparatus is an apparatus for recognizing a pattern of a fingerprint of a human finger. In order to develop a small fingerprint sensor apparatus, a semiconductor chip for a fingerprint sensor having a fingerprint sensor part formed thereon has been developed. Generally, the fingerprint sensor part is composed of a pressure sensor or a capacitance sensor, and processes information from a sensor part by a semiconductor chip so as to perform recognition and discrimination of a fingerprint. Such a semiconductor chip for a fingerprint sensor is encapsulated by a seal resin similar to regular semiconductor chips, and is incorporated into electronic equipment as a fingerprint sensor semiconductor device.
FIG. 1 is a cross-sectional view showing a resin encapsulation process in a production process of a conventional fingerprint sensor apparatus. A semiconductor element 2 for fingerprint sensors has a sensor part 4 in a circuit forming surface thereof, and electrodes are arranged around the sensor part 4. The electrodes are wire-bonded by gold wires 6 or the like to electrode pads 8a of a circuit board 8 as an interposer. The semiconductor chip 2 and the gold wires 6 are molded by a seal resin, and, thus, a seal resin part 10 is formed.
The sensor part 4 is a part on which a finger is contacted directly so as to recognize a fingerprint, and needs to be exposed from the seal resin part 10. Therefore, as shown in FIG. 1, when the semiconductor chip 2 is molded by a mold die 12, a spacer 14 is provided between the mold die 12 and the sensor part 4 so as to press the spacer 14 against the sensor part 4 so that the seal resin does not cover the surface of the sensor part 4.
The spacer 14 is formed by a material such as rubber or plastic which has elasticity to some extent, and is pressed against the sensor part 4 by the mold die 12. Thereby, the seal resin is prevented from flowing onto the surface of the sensor part during the molding process.
According to the approach of making the sensor part 4 in into the exposed state by pressing the spacer 14 during the molding process, the sensor part 4 may be damaged when the spacer 14 is pressed against the sensor part 4 if the spacer does not have an elasticity to some extent. However, if the sensor part 4 has elasticity, the seal resin may enter between the sensor part 4 and the spacer 14 due to a resin mold pressure.
FIG. 2 is a cross-sectional view of the fingerprint sensor apparatus, which is molded in a state where the seal resin enters between the sensor part 4 and the spacer 14. Opening 10a of the seal resin part 10 is formed in a part at which the spacer 14 was placed during the molding process, and the sensor part 4 is exposed within the opening 10a. 
However, as shown in FIG. 2, the seal resin which entered between the sensor part 4 and the spacer 14 serves as a mold flash 16, and adheres to the surface of the sensor part 4. For this reason, a part of the surface of the sensor part 4 is covered by the mold flash 16, and such a part may lose the function as the sensor part. That is, the area of the part, which provides the functions as a sensor part 4, may be reduced.
If the fingerprint sensor is of a so-called area type in which the sensor part 4 has a relatively large area, the remaining uncovered part can maintain the function as the sensor part since a ratio of the part covered by the mold flash is small. However, in a case of a so-called sweep-type fingerprint sensor, which reads a fingerprint by the sensor part being wiped by a finger, a width H of the sensor part 4 is very as small as 1 mm. Generally, a length L of a mold flash is 0.3 mm–0.5 mm, and a large part of the sensor part 4 may be covered by the mold flash, which results in fail in the function of the sensor part.
Additionally, in the case of the sweep-type fingerprint sensor, is a height of the resin surrounding the exposed part of the sensor part 4 is high, there is also a problem in that an operation to wipe (sweep) by a finger becomes difficult while the finger contacts the sensor part 4.